1. Technical Field
The present invention relates to a circuit for limiting current surges in general and, in particular, to a circuit for limiting current surges during hot-plugging of an adaptor card within a computer system. Still more particularly, the present invention relates to a circuit for eliminating voltage dropouts and noise transients during hot-plugging of a high-power adaptor card within a computer system.
2. Description of the Prior Art
For a computer system that is required to be in operation 24 hours a day, 365 days a year, it is imperative that any service or modification to the system can be performed in a non-disruptive manner so that the system can continue to function without any interruption. Thus, the removal and installation of various adaptor cards to the system, each having its own set of functions, from and to a respective card slot of the system are often performed under a procedure known as "hot-plugging" or "hot-swapping."
Hot-plugging allows for system serviceability or expandability without requiring an entire shutdown of the system; however, hot-plugging also exposes a powered-up system to various potential hazards. A common hazard is the generation of voltage transients on DC power supplies due to an abrupt change in load from the insertion of an adaptor card that has a high-power requirement. Momentary voltage dropouts and noise spikes can cause errors to occur in any device that shares a common power bus. Further, sudden surge currents, nearly equivalent to a short circuit, can overwhelm the power supply regulation and distribution unit of the system, which will result in power dropouts to active logic cards.
One solution to this problem would be to design the computer system to have an independent power control unit or regulator at each adaptor card slot. However, this solution seems to be wastefully expensive because a spike-avoidance device or a power control unit is required for each adaptor card slot, regardless of whether or not the adaptor card slot is currently utilized. In addition, the probability of component failure also increases accordingly as the total number of components within the system increases. Furthermore, because the system is always ready to power up adaptor cards which may never be inserted, thus this solution may also be a waste of electricity.
Consequently, it would be desirable to provide an improved circuit for minimizing or eliminating voltage dropouts and noise transients during the hot-plugging of a high-power adaptor card.